Campaign monitor has done a study about the most popular email clients used by people and the results are shown alongside. These stats are based on the email client usage of more than 300 million people that was done by Campaign Monitor for some six months.The company embeds a tracking image into their email messages and uses the referral information to determine the email client that was used to open that particular email.If you took this study in India then the difference you might see is the larger stake of gmail in the pie and lesser of hotmail but the critical information will remain that Outlook is the preferred means of everyone checking their emails. source: DI